Tom's Hardware Verdict
The Corsair AX850 is the best 850-watt PSU you can get, thanks to its high-efficiency and low noise levels, but you’ll pay a premium for it.
Pros
- +
Quiet Operation
- +
Efficient
- +
Great performance overall
- +
Long hold-up time
- +
Top build quality
- +
Ten-year warranty
Cons
- -
Expensive
- -
EPS connectors should use 16AWG wires
- -
Short distance between the peripheral connectors
- -
High OCP on the minor rails
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Specifications and Part Analysis
If you need the best 850W power supply and you don't have a restrictive budget, the AX850 should be among your top choices. It registers high performance in all areas: efficiency, load regulation, ripple suppression, transient response and, on top of that, it is dead silent as well. This unit is based on the Seasonic Prime Titanium platform, which is the best analog design today. With such great analogue platforms, someone could wonder why spend more on digital ones, where all major functions are controlled by micro-controllers instead of analogue ICs. As we see it, in the near future the AX860i will be probably replaced by the AX850, which easily meets its performance, although this is a bit of a paradox, a digital platform to get replaced by an analogue one.
We have already reviewed the AX1000, and we were impressed enough to provide it with an editor's choice award. The AX850 keeps the performance bar high as well, since it is also based on the top-notch Seasonic Prime Titanium platform. Corsair decided to cooperate again with Seasonic and this is good news in our opinion, since this manufacturer has some great designs to show.
With 80 PLUS Platinum and ETA-A+ efficiency certifications there is no doubt that the AX850 is highly efficient and the LAMBDA-A+ noise certification clearly depicts its quiet operation, even under tough conditions.
The higher the efficiency levels the lower the thermal loads, so the cooling fan has less work to do and can rotate at lower speeds. Large heat sinks can also help in this, with a recent example being the Rog Thor 1200W unit. Nonetheless, you still need high efficiency levels since if the heat sinks reach their limits, increased airflow will be needed to handle heat dissipation and keep the temperatures of the internals low.
Specifications
| Manufacturer (OEM) | Seasonic |
|---|---|
| Max. DC Output | 850W |
| Efficiency | 80 PLUS Titanium, ETA-A+ (91-94%) |
| Noise | LAMBDA-A+ (15-20 dB[A]) |
| Modular | ✓ (Fully) |
| Intel C6/C7 Power State Support | ✓ |
| Operating Temperature (Continuous Full Load) | 0 - 50°C |
| Over Voltage Protection | ✓ |
| Under Voltage Protection | ✓ |
| Over Power Protection | ✓ |
| Over Current (+12V) Protection | ✓ |
| Over Temperature Protection | ✓ |
| Short Circuit Protection | ✓ |
| Surge Protection | ✓ |
| Inrush Current Protection | ✓ |
| Fan Failure Protection | No |
| No Load Operation | ✓ |
| Cooling | 135mm Fluid Dynamic Bearing Fan (HA13525L12F-Z) |
| Semi-Passive Operation | ✓ (Selectable) |
| Dimensions (W x H x D) | 152 x 87 x 172mm |
| Weight | 2 kg (4.41 lb) |
| Form Factor | ATX12V v2.4, EPS 2.92 |
| Warranty | 10 Years |
Power Specifications
| Rail | 3.3V | 5V | 12V | 5VSB | -12V | |
|---|---|---|---|---|---|---|
| Max. Power | Amps | 20 | 20 | 70 | 3 | 0.3 |
| Watts | 100 | 840 | 15 | 3.6 | ||
| Total Max. Power (W) | 850 |
Cables & Connectors
| Modular Cables | ||||
|---|---|---|---|---|
| Description | Cable Count | Connector Count (Total) | Gauge | In Cable Capacitors |
| ATX connector 20+4 pin (610mm) | 1 | 1 | 16-20AWG | Yes |
| 4+4 pin EPS12V (650mm) | 2 | 2 | 18AWG | Yes |
| 6+2 pin PCIe (670mm+100mm) | 4 | 8 | 16-18AWG | Yes |
| SATA (460mm+110mm+110mm+110mm) | 4 | 16 | 18AWG | No |
| 4 pin Molex (550mm+100mm+100mm) | 2 | 6 | 18AWG | No |
| FDD Adapter (110mm) | 1 | 1 | 22AWG | No |
| AC Power Cord (1400mm) | 1 | 1 | 14AWG | - |
There are two EPS and eight PCIe connectors, along with 16x SATA and six 4-pin Molex. Needless to say that they are more than enough for an 850W unit. The cables are quite long but the distance between the peripheral connectors is small at only 100-110mm. Ideally it should be 150mm. Finally, we would like to see 16AWG gauges on the EPS cables for lower voltage drops at high loads.
Component Analysis
We strongly encourage you to a look at our PSUs 101 article, which provides valuable information about PSUs and their operation, allowing you to better understand the components we're about to discuss.
| General Data | |
|---|---|
| Manufacturer (OEM) | Seasonic |
| Platform Model | Prime |
| Primary Side | |
| Transient Filter | 6x Y caps, 3x X caps, 2x CM chokes, 1x MOV |
| Inrush Protection | NTC Thermistor & Relay |
| Bridge Rectifier(s) | 2x Vishay LVB2560 (600V, 25A @ 105°C) |
| APFC MOSFETS | 2x Infineon IPP60R099CP (650V, 19A @ 100°C, 0.099 Ohm) |
| APFC Boost Diode | 1x CREE C3D10060 (600V, 10A @ 153°C) |
| Hold-up Cap(s) | 2x Nippon Chemi-Con (400V, 680uF & 470uF or 1150uF combined, 2000h @ 105°C, KMR) |
| Main Switchers | 4x Infineon IPP50R140CP (550V, 15A @ 100°C, 0.140 Ohm) |
| Drivers For Main Switchers | 2x Silicon Labs Si8230BD |
| APFC Controller | ON Semiconductor NPC1654 |
| Switching Controller | Champion CM6901 |
| Topology | Primary side: Full-Bridge & LLC Resonant Converter Secondary side: Synchronous Rectification & DC-DC converters |
| Secondary Side | |
| +12V MOSFETS | 4x Infineon BSC014N04LS (40V, 100A @ 100°C, 1.4 mOhm) |
| 5V & 3.3V | DC-DC Converters: 6x Infineon BSC0906NS PWM Controller: APW7159 |
| Filtering Capacitors | Electrolytics: Nippon Chemi-Con (105°C, W, KYB) 1x Chemi-Con (5VSB circuit, 5-6,000h @ 105°C, KZH) Polymers: FPCAP, Nippon Chemi-Con |
| Supervisor IC | Weltrend WT7527V (OVP, UVP, OCP, SCP, PG ) |
| Fan Model | Hong Hua HA13525L12F-Z (135mm, 12V, 0.22A, 1600 RPM, Fluid Dynamic Bearing) |
| 5VSB Circuit | |
| Buck Converter | Leadtrend LD7750R |
| Rectifiers | STMicroelectronics STU6N65K3 (650V, 3A @ 100°C, 1.3mOhm), Infineon BSC0906NS (30V, 40A @ 100°C, 4.5mOhm) |
| -12V Circuit | |
| Buck Converter | Lite-On LSP5523 (3A max output current ) |
This is the platform used in the Seasonic Prime Titanium Ultra models, and it is considered among the best analog platforms in today's market. It uses top-quality parts including Infineon FETs, Vishay bridge rectifiers, Chemi-Con electrolytic caps and a large number of polymer caps, provided by FPCAP.
In the primary side a full-bridge topology is utilized along with an LLC resonant converter, while in the secondary side we meet a synchronous rectification scheme and a pair of DC-DC converters, which regulate the minor rails. Finally, the mid-speed cooling fan is made by Hong Hua and it uses a fluid dynamic bearing, which besides a long lifetime also provides silent operation. The highly-relaxed fan profile plays a notable part as well, in keeping the noise low.
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